Method for the manufacture of solid phosphoric acid catalyst

ABSTRACT

A process for the manufacture of a solid phosphoric acid catalyst. A siliceous adsorbent is admixed with a polyphosphoric acid. The mixture is heated at an elevated temperature and thereafter extruded. High activity - high strength extrudate particles are produced by drying the extrudate first in a steam atmosphere and then in a dry air atmosphere.

United States Patent Hovarth et a1.

[ 1 June 27, 1972 METHOD FOR THE MANUFACTURE OF SOLID PHOSPHORIC ACIDCATALYST Edward llovarth, Woodland Hills, Calif.;

Inventors:

Gary Youngman, Des Plaines, 111.

Universal Oil Products Company, Des Plaines, 111.

Filed: July 13, 1970 Appl. No.: 54,612

Assignee:

US. Cl. ..252/435, 260/683.l5 C

Int. Cl. t ..B01j 11/82 Field of Search ..252/435 [56] References CitedUNITED STATES PATENTS 2,231,452 2/1941 Morrell ..252/435 2,275,1823/1942 lpatieffet a1 ..252/435 3,213,036 10/1965 Morrell ..252/435Primary ExaminerPatrick P. Garvin Att0rneyJames R. Hoatson, Jr. andRobert W. Welch 57 ABSTRACT 6 Claims, No Drawings METHOD FOR THEMANUFACTURE OF SOLID PHOSPHORIC ACID CATALYST Hydrocarbon conversioncatalysts, and specifically olefin polymerization catalysts, haveheretofore been prepared by admixing a solid adsorbent with an oxygenacid of phosphorus and drying and calcining the resultant mixture toform a solid catalyst, usually in the extruded form. The prior artfurther discloses solid catalysts of this type which contain componentsother than the oxygen acid'of phosphorus and the solid adsorbent,examples of such components including metals such as nickel, zirconium,manganese, cobalt, or salts thereof, and also carbonaceous materialssuch as charcoal, activated charcoal, lamp black, graphite, coke,powdered coal, etc. In the manufacture of such catalyst, it has beenfound that drying of the catalyst particles in a steam atmosphere ishighly advantageous with respect to catalyst activity. However, theadvantages derived from steam drying are somewhat offset by thesubstantial reduction in particle crushing strength resulting therefrom.

it is an object of this invention to provide a process for themanufacture of a solid phosphoric acid hydrocarbon conversion catalystof improved crushing strength. It is a further object to provide a solidphosphoric acid catalyst possessing a high degree of activity withrespect to olefin polymerization and of improved crushing strength.

In one of its broad aspects, the present invention embodies a processfor the manufacture of a solid phosphoric acid catalyst which comprisesadmixing a siliceous adsorbent with an oxygen acid of phosphorus andheating the mixture at a temperature of from about 100 to about 500 F.,extruding the mixture and drying the extrudate particles in a steamatmosphere for a period of at least 0.5 hours at a temperature of fromabout 500 to about 800 F and thereafter in a dry air atmosphere for aperiod of at least about 0.5 hours at a temperature of from about 550 toabout 850 F.

One of the more specific embodiments of this invention comprisesadmixing kieselguhr with a polyphosphoric acid to form a mixturecomprising from about 60 to about 80 wt. phosphoric acid and from aboutto about 40 wt. kieselguhr, heating the mixture at a temperature of fromabout 100 to about 500 F., extruding the mixture and drying theextrudate particles in a steam atmosphere for a period of from about 0.5to about 1.5 hours at a temperature of from about 650 to about 750 F.,said steam atmosphere comprising from about 20 to about 35 wt. watervapor, thereafter drying the particles in a dry air atmosphere for aperiod of from about 0.5 to about 1.5 hours at a temperature of fromabout 700 to about 800 F.

Other objects and embodiments of this invention will become apparent inthe following detailed specification.

The essential and active ingredient of the solid catalyst hereincontemplated is an acid of phosphorus, preferably one in which thephosphorus has a valence of +5. The acid may constitute from about 60 toabout 80 wt. or more of the catalyst mixture ultimately produced, and inmost cases is over 50 wt. thereof. Of the various acids of phosphorus,orthophosphoric acid (H -,PO and pyrophosphoric acid (H P O) findgeneral application in the primary mixtures, due mainly to theircheapness and to the readiness with which they may be procured, althoughthe invention is not restricted to their use but may employ any of theother acids of phosphorus insofar as they are adaptable. It is notintended to infer, however, that the different acids of phosphorus,which may be employed will produce catalysts which have identicalaffects upon any given organic reactions as each of the catalystsproduced from different acids and by slightly varied procedure willexert its own characteristic action.

in using orthophosphoric acid as a primary ingredient, differentconcentrations of the aqueous solution may be employed fromapproximately 75 percent to 100 percent, or acid containing some freephosphorus pentoxide may even be used. By this is meant that the orthoacid may contain a definite percentage of the pyro acid corresponding tothe primary phase of dehydration of the orthophosphoric acid. Withinthese concentration ranges, the acids will be liquids of varyingviscosities, and readily mix with adsorbent materials. In practice, ithas been found that pyrophosphoric acid corresponding to the formula 11F 0 can be incorporated with siliceous adsorbents at temperaturessomewhat above its melting point (142 F.) and that the period of heatingwhich is given to the pyro acidadsorbent mixtures may be different fromthat used when the ortho acid is so employed.

. Triphosphoric acid which may be represented by the formu la H P O mayalso be used as a starting material for prepara tion of the catalyst ofthis invention. These catalytic compositions may also be prepared fromthe siliceous materials mentioned herein and phosphoric acid mixturescontaining orthophosphoric, pyrophosphoric, triphosphoric, and otherpolyphosphoric acids.

Another acid of phosphorus which may be employed in the manufacture ofcomposite catalysts according to the present invention istetraphosphoric acid. It has the general formula H P O which correspondsto the double oxide formula 3H O- 2P O which in turn may be consideredas the acid resulting when three molecules of water are lost by fourmolecules of orthophosphoric acid (H PO The tetraphosphoric acid may bemanufactured by gradual and controlled dehydration by heating oforthophosphoric acid or pyrophosphoric acid or by adding phosphoruspentoxide to these acids in proper amounts. When the latter procedure isfollowed, phosphoric anhydride is added gradually until it amounts to520 wt. of the total water present. After a considerable period ofstanding at ordinary temperatures, the crystals of the tetraphosphoricacid separate from the viscous liquid and it is found that thesecrystals melt as approximately 93 F. and have a specific gravity of1.1886 at a temperature of 60 F. However, it is unnecessary tocrystalize the tetraphosphoric acid before employing it in thepreparation of the solid catalyst inasmuch as the crude tetraphosphoricacid mixture may be incorporated with the siliceous adsorbent and othercatalyst ingredients.

The material which may be employed as adsorbents or carries for oxygenacids of phosphorus are divided roughly into two classes. The firstcomprises materials of predominantly siliceous character and includesdiatomaceous earth, Kieselguhr, and artificially prepared porous silica.The second class of materials which may be employed either alone or inconjunction with the first class comprises generally certain members ofthe class of alumina silicates and includes such naturally occurringsubstances as various fullers earth and clays such as bentonite,montmorillonite, acid treated clays and the like. Each adsorbent orsupporting material which may be used will exert its own specificinfluence upon the net effectiveness of the catalyst composite whichwill not necessarily be identical with that of other members of theclass.

The catalyst of the present invention may be prepared by admixing adiatomaceous earth, such as kieselguhr or other siliceous adsorbentmaterial, with an acid of phosphorus such as orthophosphoric acid,pyrophosphoric acid, triphosphoric acid or tetraphosphoric acid. Thestarting materials used in this catalyst preparation process aregenerally mixed at a temperature of from about to about 500 .F. to forman aggregate in which the phosphoric acid content is usually a majorportion by weight, although a temperature in the upper range of fromabout 200 to about 500 F. is often needed. The aggregate formed by thephosphoric acids and the siliceous adsorbent is a slightly moist toalmost dry material which on being compressed becomes sufficientlyplastic to permit extrusion and cutting operations to produce catalystparticles.

The conditions at which the wet extrudate particles are subsequentlydried have been observed to have a significant and substantial effect onthe properties of the finished catalyst. For example, it has beenobserved that a drying atmosphere having a high moisture content tendsto produce a catalyst product of relatively high activity. However,coupled with the high activity is a substantial loss in crushingstrength of the catalyst particles. A unique two-step drying sequencehas now been discovered whereby the improved catalyst activity, affordedthrough utilization of-a'high moisture content drying atmosphere, isretained without sacrificing the crushing strength of the catalystparticles. Thus, it has been discovered that drying the extrudateparticles first in a steam atmosphere and then in a dry "air atmospherewill yield an extrudate product of high activity as well as crushingstrength. ln accordance with the present invention, the extrudateparticles are dried in a steam atmosphere fora period of at least about0.5 hours at a temperature of from about 500 to about 800 F. andthereafter in a dry air atmospherefor a period of at least about 0.5hours at a temperature of from about 550 to about 850 F. In a preferredembodiment, the extrudate particles are dried in a steam atmosphere fora period of from about 0.5 to

' about 1.5 hours at atemperature of from about 650 to about 750 F.andthereafter in a dry air atmosphere for a period of from about 0.5 toabout 1.5 hours at a temperature of from about 700 to about800 F theaforesaid steam atmosphere comprising from about 20 to about 30 wt. ormore water vapor. The catalyst thus prepared is active for promoting thepolymerization of olefinic hydrocarbons, particularly for polymerizingnormally aqueous olefinic hydrocarbons to form normally liquidhydrocarbons suitablefor use as constituents of gasoline. When employedin the conversion of olefinic hydrocarbons into polymers, the catalystformed as heretofore set forth, is preferably employed as a granularlayer in a heated reactor which is generally made from steel, andthrough which the preheated hydrocarbon fraction is directed. Thus, thesolid catalyst of this process may be employed for treating mixtures ofolefin-containing hydrocarbon vapors to effect olefin polymerization,but the same catalyst may also be used at operating conditions suitablefor maintaining liquid phase operation during polymerization of olefinichydrocarbons, such as butylenes, to produce gasoline fractions. Whenemployed in the polymerization of normally gaseous olefins, the formedcatalyst particles are generally placed in a vertical, cylindricaltreating tower and the olefin-containing gas mixture is passeddownwardly therethrough at a temperature of from about 350 to about 550F. and at a pressure of from about 100 to about 1,500 psi.- Theseconditions are particu larly applicable when dealing witholefin-containing material such as stabilizer reflux which may containfrom approximately to 50 percent or more of propylene and butylenes.When operating on a mixture cornprising essentially propylene andbutylenes, this catalyst is effective at conditions favoring. themaximum utilization of both normal butylene and isobutylene whichinvolves mixed polymerization at temperatures of from about 250 to about325 F. and at a pressure of from about 500 to about 1,500 psi.

The catalyst of this invention, when being used for p'romotingmiscellaneous organic reactions, will be employed in essentially thesame way as they are used when polymerizing olefins, in that thereactions are essentially in the vapor phase, and that they also may beemployed in suspension in liquid phase and various types of equipment.

With suitable modifications in the details of operation, the presenttype of catalyst may be employed in a large number of organic reactionsincluding polymerization of olefins as already mentioned. Typicalreactions for which the present type of catalyst may be used include thealkylation of cyclic compounds with olefins, the cyclic compoundsincluding aromatics, polycyclic compounds, naphthenes, and phenols;condensation reactions such as those occurring between ethers andaromatics, alcohols and aromatics, phenols and aldehydes, etc.;reactions involving the hydrohalogenation of unsaturated organiccompounds, isomerization reactions; ester formation by the interactionof carboxcyclic acids and olefins; and the like. The specific proceduresfor utilizing the present type of catalyst in miscellaneous organicreactions will be determined by the chemical and physicalcharacteristics and the phase of the reacting constituents.

During use of these catalysts in vapor phase polymerization and othervapor phase treatments of organic compounds, it is often of value to addsmall amounts of moisture to prevent excessive dehydration andsubsequent decrease in catalyst activity and in order to substantiallyprevent loss of water from the catalyst. An amount of water or watervapor such as steam is added to the charged olefin-containing gas soas'to substantially balance the vapor pressure of the catalyst. Thisamount of water vapor varies from about 0.1 to about 6 percent by volumeof the organic material charged.

The following examples are presented in illustration of the method ofthis invention and are not intended'as an undue limitationon thegenerally broad scope of the invention as set out in the appendedclaims.

EXAMPLE! date particles dried for 70 minutes at 700 F. with aircontaining about percent water vapor, the hot gases being passedupwardly through the extrudate particles distributed in a rnov-' ingbelt conveyor. The crushing strength of the catalyst particles was 21.7lbs., the crushing strength of this and subsequent catalysts beingdetermined with an apparatus constructed to apply force continuouslyandat a unifonn rate beginning with a zero load. The crushing strengthwas determined as the arithmetic average of the force required to crusheach particle of a given member of individual particles. 1

The catalyst thus prepared was placed in a fixed bed of a verticaltubular reactor and a light hydrocarbon feed stock comprising 37percent. olefins as propylene was continuously charged thereto in aonce-through type of operation. The gaseous hydrocarbon feed stock wascharged upflow through the catalyst bed at a gaseous hourly spacevelocity of 0.2, the reactor being maintained at about 1,000 psi. and ata temperature of 400 F. A 76 percent conversion of propylene topropylene polymer was achieved in this once-through type of operation. I

EXAMPLE ll A solid phosphoric acid catalyst was prepared substantiallyas described in the previous example except that the steam dried productwas further dried in a batch kiln for minutes at 750 F. in a dry airatmosphere. In this instance, the crushing strength of the extrudateparticles averaged 36.5 lbs. as opposed to 21.7 lbs. of the previousexample, and a 78 percent conversion of propylene to propylene. polymerat the conditions of the proceding example.

We claim as our invention:

1. ln a process for the manufacture of a solid phosphoric acid catalystwhich comprises admixing a diatomaceous earth with an oxygen acid ofphosphorus in proportions to form a mixture comprising from about 60 toabout 80 wt. oxygen acid of phosphorus and from about 20 to about 40 wt.diatomaceous earth, heating the mixture at a temperature of from aboutto about 500 F., extruding the mixture and drying the extrudateparticles the improvement which comprises drying the resulting wetextrudate particles in a steam atmosphere for a period of at least about0.5 hours at a temperature of from about 500 to about 800 F., andthereafter in a dry air atmosphere for a period of at least about 0.5hours at a temperature of from about 550 to about 850 F.

2. The process of claim 1 further characterized in that. said oxygenacid of phosphorus is a polyphosphoric acid.

3. The process of claim 1 further characterized in that said mixture isheated at a temperature of from about 250 to about 450 F.

4.'The process of claim 1 further characterized'in that said extrudateparticles are dried in a steam atmosphere for a period of at least about0.5 hours ata temperature of from about 650 to about 750 F. andthereafter in a dry air atfor a period of from about 0.5 to about 1.5hours.

6. The process of claim 1 further characterized in that said steamatmosphere comprises from about 20 to about 35 wt.

water vapor.

2. The process of claim 1 further characterized in that said oxygen acidof phosphorus is a polyphosphoric acid.
 3. The process of claim 1further characterized in that said mixture is heated at a temperature offrom about 250* to about 450* F.
 4. The process of claim 1 furthercharacterized in that said extrudate particles are dried in a steamatmosphere for a period of at least about 0.5 hours at a temperature offrom about 650* to about 750* F. and thereafter in a dry air atmospherefor a period of at least about 0.5 hours at a temperature of from about700* to about 800* F.
 5. The process of claim 1 further characterized inthat said extrudate particles are dried in said steam atmosphere at saidtemperature for a period of from about 0.5 to about 1.5 hours andthereafter in said dry air atmosphere at said temperature for a periodof from about 0.5 to about 1.5 hours.
 6. The process of claim 1 furthercharacterized in that said steam atmosphere comprises from about 20 toabout 35 wt. % water vapor.